# Flow‐Induced Microdomain Alignment During Block Copolymer Graphoepitaxy

## TL;DR

This study explores how polymer flow during a nanofabrication process affects the alignment of tiny structures on patterned surfaces.

## Contribution

The study reveals how flow processes during solvent vapor annealing influence microdomain orientation in block copolymer graphoepitaxy.

## Key findings

- Capillary flow in the first minute of annealing planarizes the film into an incommensurate thickness.
- Isotropic dewetting produces microdomains transverse to trench sidewalls, while anisotropic dewetting promotes alignment parallel to the walls.
- The study demonstrates a connection between flow-induced microdomain alignment, film thickness, and trench depth.

## Abstract

Block copolymer (BCP) graphoepitaxy provides a strategy for advanced nanofabrication based on self‐assembly. However, the polymer flow processes that occur due to the topography of the substrates and their effects on the self‐assembled microdomain patterns are not well understood. Here, by analyzing film thickness profiles and microdomain morphologies as a function of time during solvent vapor annealing, the time scale of the flow processes (capillary flow and dewetting) and how they determine the in‐plane orientation of cylindrical microdomains with respect to the sidewalls of trenches etched in the substrate are revealed. Capillary flow in the first minute of annealing planarizes the film into an incommensurate thickness. The film then dewets through nucleation and growth of islands and holes, which extend either isotropically or anisotropically along the trench axis, depending on film thickness. Isotropic dewetting produces microdomains, which are primarily transverse to the trench sidewalls, whereas anisotropic dewetting promotes alignment parallel to the trench walls. This study demonstrates an intriguing connection between flow‐induced microdomain alignment, film thickness, and trench depth during BCP graphoepitaxy, revealing general principles for controlling BCP microdomain orientation over topographical templates.

This study investigates block copolymer flow on topographical templates during solvent vapor annealing and how flow affects the orientation of self‐assembled microdomains. The temporal mapping between flows and microdomain orientation reveals an intriguing dependence of flow‐induced microdomain alignment on film thickness and trench depth, and provides a general principle for microdomain orientation control in block copolymer graphoepitaxy‐based nanofabrication.